The invention pertains to a coated article, as well as a method for applying the coating scheme. More specifically, the invention pertains to a coated article wherein the coating scheme includes nanolayers containing aluminum, chromium, titanium and nitrogen, as well as a method for applying the coating scheme. Exemplary coated articles include without limitation cutting inserts and wear components.
Referring to a coated cutting insert as one example of a coated article, a coated cutting insert typically comprises a substrate with a coating scheme thereon. The cutting insert exhibits a geometry such that it typically has rake surfaces and flank surfaces wherein there are cutting edges at the intersection (or juncture) of the rake surfaces and the flank surfaces. For coated cutting inserts in general, any one of a number of different techniques can apply the coating scheme to the substrate. These techniques can include chemical vapor deposition (CVD) and physical vapor deposition (PVD).
Coated cutting inserts are useful for the removal of material in a chipforming material removal operation. Chipforming material removal operations include, without limitation, milling, turning, boring, drilling and like operations wherein a cutting insert engages a workpiece with the cutting insert and workpiece moving relative to each other. A great amount of heat can exist at the point (or surface) of engagement between the workpiece and cutting insert (i.e., cutting insert-chip interface). Transfer of the heat at the cutting-chip interface into the substrate and the interface between the coating scheme and the substrate (i.e., coating-substrate interface) can be detrimental to cutting insert performance. More specifically, transfer of heat to the substrate and the coating-substrate interface creates premature excessive wear of the coating. Such excessive wear of the coating scheme typically shortens the useful life of the coated cutting insert.
The coating scheme typically influences the extent of heat transfer from the cutting insert-chip interface to the substrate and coating-substrate interface. The thermal conductivity of the coating scheme is a property that can strongly influence the extent of such heat transfer. A coating scheme that exhibits an overall lower thermal conductivity typically reduces the amount of heat in the substrate and at the coating-substrate interface. Such a reduction in heat transfer typically results in a longer useful tool life for the cutting insert in comparison to a coated cutting insert that does not exhibit a reduction in heat transfer.
In the past, coated cutting inserts have exhibited various coating schemes. For example, U.S. Patent Application Publication No. US 2006/0269788 A1 to Ishikawa appears to disclose alternating layers of AlCrTiN with differing compositions between the layers. According to the English abstracts, Japanese Patent Publication No. 2003 340608 A2 to Natsuki et al. and Japanese Patent Publication No. 2004 106108 A2 to Hidemitsu et al. each provide a disclosure that appears to include alternating layers of TiAlCrN, but the chromium is always present in each coating layer.
WO 2006/084404 A1 to Endrino (assigned to Uniaxis Balzer AG) appears to disclose the use of an AlCrN inner coating layer and an AlCrN outer coating layer. According to the English abstract, Japanese Patent Publication No. 2004 050381 A2 to Yasuhiko apparently discloses a surface layer of AlCrN. U.S. Pat. No. 7,226,670 B2 to Derflinger et al. (assigned to OC Oerlikon Balzers AG) appears to teach that AlCrN is a beneficial coating material.
U.S. Patent Application Publication No. US 2005/0170162 A1 to Yamamoto et al. apparently discloses a coating layer of (Ti Al Cr)N in an alternating coating scheme. U.S. Pat. No. 6,730,392 B2 to Vetter et al. seems to disclose an alternating coating scheme wherein the layers have different contents of aluminum, titanium and chromium, as well as different nitrogen/oxygen ratios. U.S. Pat. No. 7,008,688 B2 to Toihara appears to show alternating coating layer arrangement using TiAlN and CrN. Further, the following patent documents seems to show various coating schemes with alternating coating layers: U.S. Pat. No. 6,103,357 to Selinder et al., U.S. Pat. No. 7,056,602 to Hörling et al., U.S. Pat. No. 7,083,868 to Hörling et al., and PCT Patent Publication WO 2006/041366 A1 to Astrand et al.
The following three patents apparently show the utility of (Ti Al Cr)N films: U.S. Pat. No. 6,824,601 B2 to Yamamoto et al., U.S. Pat. No. 6,919,288 B2 to Yamamoto et al., and U.S. Pat. No. 7,186,324 B2 to Yamamoto et al.